Do Now

1. Do Now _____ female reproductive struture of a flower _____1 cotyledon _____type of root that has several roots of the same size that spread out _____male reproductive structure of a flower _____an area in space that has very strong gravity and nothing can escape

2. Key Questions What is heredity? What is a trait? What is the difference between a dominant and recessive trait? What is gene? What is an allele? What is a dominant allele? What is a recessive allele?

3. Section 1 • 1. Heredity is the passing of traits from parents to offspring. • Why then do you some of you have curly hair while both your parents have straight hair? • Why does someone have blue eyes when both parents have brown eyes?

4. Key Question • Who is Gregor Mendel and what experiments is he famous for?

5. Section 1 continued • About 150 years ago some very important experiments were performed that helped scientists find some answers to these problems. • The person who performed these experiments was Gregor Mendel.

6. Section 1 continued • Who was Gregor Mendel? • He was born in Austria in 1822, and studied at University after which, he went into the monastery and studied plants in the gardens. • Specifically he studied how traits are passed between parents and offspring. • He noticed that sometimes a trait showed up in one generation, but not the next, and in the third generation the trait showed up again.

7. Section 1 continued • Mendel noticed the same patterns in people, plants, and many other living things. • To simplify his investigation, he decided to study only one kind of organism. • He had already studied the garden pea plant, so he chose this as his subject. • Garden peas were a good choice for several reasons, they grow quickly, they are self pollinating, and they come in many varieties.

8. Section 1 continued • Self pollinating plants contain both male and female reproductive structures. • Pollination can be either by wind or animals, such as a bee. • Pollen from the anthers(male)is transferred to the stigma(female). • Fertilization occurs when a sperm from the pollen travels through the stigma and enters the egg in the ovule.

9. Section 1 continued • Mendel chose to study only one characteristic at a time, such as plant height, color, or seed shape. • Each characteristic had only two options. For height, short or tall, for color white or purple, for seed shape round or wrinkled.

10. Section 1 continued • Mendel used plants that were true breeding for each of the traits he was studying. • When a true breeding plant self pollinates it will always produce offspring with the same trait the parent has. • A tall true breeding plant will always produce offspring that are tall.

11. Section 1 continued • He decided to find out what would happen if he crossed two plants that had different forms of a single trait. • To do this he would have to use a method called cross-pollination. • In cross-pollination, the anthers from one plant are removed so that the plant cannot self-pollinate.

12. Section 1 continued • The pollen from another plant is used to fertilize the plant without anthers. • This way Mendel could select which pollen would fertilize which plant.

13. Mendel’s First Experiment • He cross-pollinated a plant with round seeds with one of wrinkled seeds. • First Generation-all round seeds • Second Generation-for every three round seeds, there was one wrinkled seed.

14. Mendel’s First Experiment • 2.Trait-a distinguished quality that can be passed from one generation to another • 3. Dominant trait: One trait always appeared, and the other trait vanished • Recessive trait: The other trait seemed to recede into the background .

15. Mendel’s Second Experiment • Mendel allowed the first generation from each seven crosses to self-pollinate. • This time the plant with the dominant trait for seed shape was allowed to self-pollinate. • The wrinkled seeds showed up again.

16. It’s all in the Calvin Klein’s • Mendel realized that his results could only be explained if each plant had two sets of instructions for each characteristic. • 4. Genes-set of instructions donated by e each partent • The fertilized egg would then have two forms of the same gene for every characteristic, one from each parent. • 5. allele-two forms of the same gene

17. The Proof is in the Punnett • 6. Dominant alleles occur most often and are symbolized with capital letters. • 7. Recessive alleles occur less often and are symbolized with lower case letters.

18. Do Now _____tip of the pistil _____2 cotyledon _____type of root that grows downward and has 1 main root _____thin stalk of the stamen _____loops of gas that jump from sunspots

19. What is a punnett square? • What is a genotype? • What is a phenotype?

20. 1. A punnett square is used to visualize all the possible combinations of alleles from the parents.

21. The Proof is in the Punnett • The basic naked punnett square looks like this:

22. The Proof is in the Punnett • 2. Genotype -the inherited combination of alleles. • 3. Phenotype-the organisms appearance.

23. The Proof is in the Punnett • Lets take for example the red throated bird, where red throat is the dominant trait and a white throat is the recessive trait. • Red throat and white throat are alleles(two forms of the same gene), we abbreviate them with two forms of the same letter. So we use R for the dominant allele/trait(red throat), and r for the recessive allele/trait(white throat).

24. The Proof is in the Punnett • Our possible genotypes and phenotypes would look like this:

25. The Proof is in the Punnett • Remember that we don’t use R for red and W for white because that would make it two different genes which would code for two different traits, and throat color is one trait. What the genotype contains are two codes for the same trait, so we use two forms of the same letter.

26. The Proof is in the Punnett • A very, very helpful thing to memorize is that the only way for a recessive trait to show up in an organism is if that organism’s genotype is homozygous recessive (two little letters, like rr)

27. The Proof is in the Punnett • Here are the basic steps to using a punnett square when solving genetics questions. After you get good at this you should never miss a genetics question involving the cross of two organisms. • 1. Determine the genotypes of the parent organisms • 2. Write down your cross(mating)

28. The Proof is in the Punnett • 3. Draw a punnett square. • 4. Split the letters of the genotype for each parent and put them outside the p-square. • 5. Determine the possible genotypes of the offspring by filling in the p-square. • 6. Summarize the results.(genotypes and phenotypes of offspring) • 7. Bask in the glow of your accomplishment.

29. The Proof is in the PunnettStep 1 • Determine the genotypes of the parent organism.(could be given or in a word problem) • Make sure you understand the vocabulary • 5. Homozygous=when both alleles of a pair are the same TT or tt • 6. Heterozygous=when both alleles of a pair are different Tt • Homozygous recessive=tt • T=tall t=short

30. The Proof is in the PunnettStep 1 continued • We are going to do a p-square on the following word problem: “Cross a short pea plant with one that is heterozygous for tallness.”

31. The Proof is in the PunnettStep 2 • Write down your “cross” (mating) • In this case it would be Tt x tt

32. The Proof is in the PunnettStep 3 • Draw a p-square.

33. The Proof is in the PunnettStep 4 • Split the letters for each parent and put them outside the the p-square. • tt • Tt

34. The Proof is in the PunnettStep 4 Con’t(remember this) • Notice that we took the letters of one parent, split them and put them on the left, outside the rows of the p-square. • Then we took the letters of the second parent, split them, and put them above the two top rows of the p-square.

36. The Proof is in the PunnettStep 5 • Determine the possible genotypes of the offspring by filling in the p-square. The next four slides will show how this works! • Remember the following, “one from the left, one from the top.”

41. The Proof is in the PunnettStep 6 • Summarize the results.(genotypes and phenotypes of offspring) • Simply report what you came up with. You should always have two letters in each of the four boxes. • In this example of Tt tall and tt short, we get 2 out of 4 boxes with Tt(tall) and we get 2 out of 4 with tt(short). • The summary would look something like this:

43. Scientific Side Note • Remember in step 4 when we split the letters of the genotypes and put them outside the p-square. What this illustrates is the process called gametogenesis(the production of sex cells, egg and sperm) Gametogenesis is a cell division thing, also called meiosis, that divides an organisms chromosome number in half.